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Old 01-12-2021, 04:14 PM   #1
dz1087
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Brake Light/Rear Turn Signal Issue

Just found out I have an issue with my rear brake lights/turn signals. The problem is when the right turn signal is on, and the brakes are applied, the left brake light turns off. Otherwise, everything works as it should. Both brake lights come on fully when the brake is applied. When the lights are on, the rear lights come on fine. Also, when the lights are on, and the right turn signal is activated, and the brakes are applied, the left parking light coil (the dimmer of the two in the rear bulb) will stay on, but the brighter brake light coil will not illuminate.

No issues when the left turn signal is activated - everything works.


Specs:
AAW wiring harness, installed last spring.
Bed center crossmember is grounded to frame.
Frame is grounded to engine.
Engine is connected to battery negative terminal.

Thoughts? Is there an easy way to determine I need a new turn signal switch vs a ground issue?
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Old 01-12-2021, 04:30 PM   #2
67C10Step
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Re: Brake Light/Rear Turn Signal Issue

Sounds like a ground issue to me. I'd probably start by running a dedicated ground wire from each tail light to a known good ground area and see if the issue remains or clears up.
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Old 01-12-2021, 07:52 PM   #3
pjmoreland
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Re: Brake Light/Rear Turn Signal Issue

It could also be that your turn signal switch contacts are gummed up.
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Old 01-13-2021, 07:08 PM   #4
dz1087
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Re: Brake Light/Rear Turn Signal Issue

Just got done testing the tail light assemblies. Both have good ground, verified with multimeter with positive probe in the sockets and negative probe touching the housing.

Leaves me thinking is the switch, unless you fellers can think of anything else.
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Old 01-13-2021, 07:15 PM   #5
Andy4639
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Thumbs up Re: Brake Light/Rear Turn Signal Issue

Have you checked the bulb? Have you checked the socket? I have seen the sockets get wear and the bulb want stay in place. I've seen the bulb tabs fall off and not work. Check all the easy stuff first. Have you done any work on any of the electrical system latey?
Your brake lights and turn signals all go through the wiring harness in the steering column. Could be a wire issue outer sleeve worn through touching metal are a turn signal cam problem. Could be the bulb itself even. I'd start at the column harness connector and probe the wires that go to the rear of the truck with it in the position that gives you the problem and probe the wires and see if it does the same there if not keep moving towards the back of the truck and see where it starts being a problem.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver
Seeing the USA in a 71


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Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 01-13-2021, 08:02 PM   #6
dz1087
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Re: Brake Light/Rear Turn Signal Issue

The sockets are new and work fine, bulbs are fine.
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Old 01-13-2021, 11:50 PM   #7
RustyPile
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Re: Brake Light/Rear Turn Signal Issue

Quote:
Originally Posted by dz1087 View Post
Just got done testing the tail light assemblies. Both have good ground, verified with multimeter with positive probe in the sockets and negative probe touching the housing.

Leaves me thinking is the switch, unless you fellers can think of anything else.
That test only verifies good contact between the socket and housing.. You also need good grounding contact between the housing and bed, between the bed and frame, and lastly, between frame and negative battery post.. A quick method to test for loss of ground is to run a long jumper directly from the negative battery post and the bulb socket.. Don't depend on twisting the wires to make contact.. Use those larger alligator clips found on small battery charger/tenders.. Hook up the jumper and try those lights again.. If they work as they should, you definitely have a grounding issue..
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Old 01-14-2021, 03:12 AM   #8
REDROCKER652002
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Re: Brake Light/Rear Turn Signal Issue

My son's truck had a somewhat similar issue. It turned out the connection wire at the bulb housing had come loose. In other words, the three wires that go into the plastic plug that plugs into the back of the taillight, one of those wires had come loose and was not making a connection. Not sure if that is even close to what you are experiencing, but what the heck. I figure I would throw it out there.
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Old 01-14-2021, 10:08 AM   #9
dz1087
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Re: Brake Light/Rear Turn Signal Issue

Quote:
Originally Posted by RustyPile View Post
That test only verifies good contact between the socket and housing.. You also need good grounding contact between the housing and bed, between the bed and frame, and lastly, between frame and negative battery post.. A quick method to test for loss of ground is to run a long jumper directly from the negative battery post and the bulb socket.. Don't depend on twisting the wires to make contact.. Use those larger alligator clips found on small battery charger/tenders.. Hook up the jumper and try those lights again.. If they work as they should, you definitely have a grounding issue..

I disagree. The circuit would have to be complete in order for the multimeter to sense a difference in the potential energy between the socket and the housing. If the housing were not grounded, the multimeter would have read zero.

Regardless, with the two-wire setup on the tail lights (one pos wire for the parking lamps and one for the brake lights), a ground failure would prevent the bulbs from turning on at all. I've got good brake lights and good parking lights on both sides. The left brake light fails to come on only if the right turn signal circuit is activated.
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Old 01-14-2021, 11:12 AM   #10
Andy4639
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Thumbs up Re: Brake Light/Rear Turn Signal Issue

Quote:
Originally Posted by dz1087 View Post
I disagree. The circuit would have to be complete in order for the multimeter to sense a difference in the potential energy between the socket and the housing. If the housing were not grounded, the multimeter would have read zero.

Regardless, with the two-wire setup on the tail lights (one pos wire for the parking lamps and one for the brake lights), a ground failure would prevent the bulbs from turning on at all. I've got good brake lights and good parking lights on both sides. The left brake light fails to come on only if the right turn signal circuit is activated.
There again the turn signal connector looking like the problem. Check it out.
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver
Seeing the USA in a 71


Upstate SC GM Truck Club
2013,14 and 2016 Hot Rod Pour Tour


http://upstategmtrucks.com/



Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 01-14-2021, 02:36 PM   #11
dz1087
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Re: Brake Light/Rear Turn Signal Issue

Quote:
Originally Posted by Andy4639 View Post
There again the turn signal connector looking like the problem. Check it out.
I'll dig in to it today. If the problem manifests at the connector, is it safe to assume switch, or are there other grounds up in there that may be buggered up? The steering column is about the only thing I haven't torn apart on this truck yet.
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Old 01-14-2021, 05:12 PM   #12
Andy4639
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Thumbs up Re: Brake Light/Rear Turn Signal Issue

Quote:
Originally Posted by dz1087 View Post
I'll dig in to it today. If the problem manifests at the connector, is it safe to assume switch, or are there other grounds up in there that may be buggered up? The steering column is about the only thing I haven't torn apart on this truck yet.
The only ground inside the steering column is for the horn button.
__________________
1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver
Seeing the USA in a 71


Upstate SC GM Truck Club
2013,14 and 2016 Hot Rod Pour Tour


http://upstategmtrucks.com/



Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
Andy4639 is offline   Reply With Quote
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